When horses are poisoned by strychnia it is either the result of malicious administration, or brought about by an overdose, or by the accidental admixture of some preparation with food, which was intended for the destruction of rats and other vermin on infested premises. Horses vary in their susceptibility to strychnia, some being acted upon by very small doses, which others take with impunity; this being so, the greatest care should be observed in its use, and none but the professional man should undertake to prescribe it. Again, indifference to plainly printed instructions or written labels is so common, and not confined to the wholly illiterate, that entire packets of "vermin-killer" have been given in a mash in lieu of alterative powders, some of which are very similar in colour and appearance.
Fig. 455. - Foxglove (Digitalis purpurea).
Unless the stomach is quite empty, and the drug taken in solution, its effects are not manifest for some twenty minutes. Rest-lessness and excitement, with an exalted sense of hearing and vision, are observed in the first instance, the movements of the animal are spasmodic and involuntary, suddenly terminating in fits of tetanic spasm, in which the animal falls to the ground and becomes perfectly rigid; relaxation of the spasm and a state of quiet may follow, but if touched ever so lightly a new paroxysm is commenced. After a variable period, according to the amount and intensity of the poisoning, the spasm is relaxed, and beyond the hurried breathing and appearance of having undergone some recent extraordinary excitement, the patient appears to be nearly well. The remission is, however, but temporary, similar seizures follow again and again, and in one of them the animal may die, or, the intervals between them becoming longer, and the paroxysms less violent, recovery follows.
The most potent antidote to this form of poisoning is chloroform, inhaled to the point of insensibility, and repeated with the recurrence of each spasm. It may be truly said that there is absolutely no danger of overdoing it until complete relaxation of the spasm indicates its withdrawal.
In the intervals, if practicable, large doses of animal charcoal and tannic acid may be given in the form of a drench, with water, and alternated with bold doses of chloral and bromide of potassium. It is quite possible with these remedies at hand to effect a cure even when a fatal dose has been taken, but it seldom happens that skilled professional assistance can be soon enough obtained. Soot and water may be used in place of charcoal, and absolute quiet enjoined until a veterinary surgeon arrives.